Aging contributes to changes in postural control, and older adults are less stable and more prone to falls than young adults. Many older people who experience a fall often have sensory deficits that impair balance, such as vestibular dysfunction. Accordingly, the development of a balance prosthesis that can provide additional sensory information about balance has clear clinical importance for older persons at risk for falls. Sensory substitution balance prostheses aim to augment sensory information available for balance in order to compensate for lost or diminished natural sensory function. Vibro-tactile feedback has been shown to be effective at reducing low frequency body sway (below about 0.5 Hz) in response to balance perturbations while standing. However, current devices tend to cause an undesirable increase in high frequency body sway, which is arguably counter to the aim of improving stability, especially in older adults, who are more prone to falls, and already sway more than young adults at higher frequencies. In addition, unlike other sensory prostheses such as hearing aids, which are fine-tuned to the user, current vibro-tactile balance prostheses largely employ a one size fits all approach, in that they use the same settings (i.e. parameter values) for all subjects. Our analysis has shown that this approach contributes to increased high frequency body sway, and that a subject-specific design is required to improve stability over a broader range of frequencies and, especially, to not increase sway at high frequencies. In this research, we aim to implement, using engineering system identification methods, and test a novel subject-specific vibrotactile feedback (VTF) design that will reduce high frequency postural sway of older adults in response to balance perturbations while standing. Reducing high frequency sway in older adults will cause their sway to look more like the natural sway of young adults, and should reduce fall risk, which has been associated with high frequency sway. The proposed research is a necessary first step to assess the feasibility of developing a user-customized VTF prosthesis, to achieve specific reductions in body sway and increased stability in older adults while standing. The knowledge to be gained in this study should be useful for advancing the use of VTF for more complex postural control tasks. PUBLIC HEALTH RELEVANCE: Falls are a major source of injury among older adults, resulting in billions of dollars in annual medical costs and adversely affecting a person's health and quality of life. One factor contributing to falls is declines in sensory function. Sensory substitution devices, such as vibrotactile feedback about body position and motion, have become of recent interest as a balance prosthesis. This research addresses the question of whether these devices can be designed to cause frequency-selective changes in body sway, in order to reduce the high frequency sway of older persons, which has been associated with fall risk.